1 Exploring Zero Discharge Potentials for the Sustainability of a ...

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Figure 5 Design schematic of the DF/IE system for final rinse recovery The overall impact of this alternative on the water balance of the plant will be similar to that of the MF/RO system. Raw water input will be reduced to 57% and the make-up rinse water for the bottle washers will be reduced by 53%. While liquid discharge will be reduced by 80.5% using this water recovery strategy , there will be additional wastewater produced loaded with NaCl due to the introduction of 35% HCl solution for resin regeneration. Designing a scheme for reduced water consumption and wastewater generation for a specific plant often requires a compromise among water quality needs, wastewater constituents, operating costs and capital equpment costs. A comparison of the two proposed rinse water recovery systems is presented in Table 3. Each alternative has its own pros and cons - choosing an optimum system is simply a matter of corporate decision among the company executives. CONCLUSIONS Table 3. Comparison of proposed rinse water recovery systems PARAMETER MF/RO DF/IE System System 1. Raw water consumption (m 3 /d) 2,350 2,388 2. Water discharged to river (m 3 /d) 740 779 3. Soft water recovered (m 3 /d) 948 912 4. Caustic soda recovered (kg/d) 170 0 5. Installation cost (Baht/ BW unit) 4,200,000 1,780,000 6. Net annual savings (Baht/ BW unit) 1,322,000 525,184 7 Net Present Value (Baht/BW unit) 5,500,000 2,200,000 8. Payback period (years/ BW unit) 3.2 3.4 9. Internal rate of return (%/ BW unit) 31.3 30.5 Water consumption profile of a softdrink plant in Bangkok revealed that raw water is drawn from deepwells at an average rate of 5,598 m 3 /d. Out of this volume, 31.3% (1,751 m 3 /d) is consumed as pre-treated process water, 21.9% (1,226 m 3 /d) as treated water and 40.3% (2,254 m 3 /d) as soft water. The amount of wastewater treated in the biological WWTP averages 4,243 m 3 /d, of which 40% comes from the bottle washing units. Given the water consumption and wastewater generation profiles, the zero discharge potentials of the bottle washing plant were explored. This enabled the plant to confront the problem of limited expansion plans with the imposition of a government restriction on digging more wells around Metropolitan Bangkok. Water recovery and reuse strategies drawn that would lead to zero discharge include polishing of the WWTP effluent by MF and purification of the final rinse effluent from the bottle washing units using two types of systems. Microfiltration of WWTP effluent and recycling of the permeate in unit processes which are not directly in contact with the product leads to cosiderable reductions in raw water input by 40% and liquid discharged to the river by 56%. There are two proposed alternatives for purification of final rinse effluent for reuse in bottle washing units. These 8
are by MF/RO system and DF/IE system. The MF/RO system recovers pure water and caustic solution in the process. This membrane application can reduce groundwater input by 58% and liquid discharged to the receiving water by 81.5%. On the other hand, treatment of rinse water by DF/IE recovers only water. The employment of such a technology will reduce water input to 57% and the liquid discharge by 80.5%. REFERENCES DMR (Department of Mineral Resources). (1995). Document on state of groundwater souces in Bankok, Thailand. Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. (1985). Environmental Engineering. Singapore: Mc-Graw-Hill Book Co. Tay, J. and Jeyaseelan, S. (1994). Reuse of Wastewater from Beverage Industry by Membrane Filtration. Proceedings of the ASEAN-Europe Workshop on Membrane Technology in Agro-based Industry, 26-30 July 1994, KL, Malaysia, pp. 28-43. 9
Page 1 and 2: ABSTRACT Exploring Zero Discharge P
Page 3 and 4: indicate that one liter of beverage
Page 5 and 6: Microfiltration (MF) of WWTP efflue
Page 7: Figure 3: Schematic of the proposed

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